High-bandwidth underwater data communication system

ABSTRACT

An apparatus is described which uses directly modulated InGaN Light-Emitting Diodes (LEDs) or InGaN lasers as the transmitters for an underwater data-communication device. The receiver uses automatic gain control to facilitate performance of the apparatus over a wide-range of distances and water turbidities.

CROSS-REFERENCES TO RELATED APPLICATIONS

This application claims the benefit of priority under 35 U.S.C. § 120 asa continuation of U.S. patent application Ser. No. 16/745,902, filedJan. 17, 2020, which claims the benefit of priority under 35 U.S.C. §120 as a continuation of U.S. patent application Ser. No. 16/405,710,filed May 7, 2019, which claims the benefit of priority under 35 U.S.C.§ 120 as a continuation of U.S. patent application Ser. No. 15/334,486,filed Oct. 26, 2016, which claims the benefit of priority under 35U.S.C. § 120 as a continuation of U.S. patent application Ser. No.13/843,942, filed Mar. 15, 2013 and that issued as U.S. Pat. No.9,490,910 on Nov. 8, 2016, each of which are hereby incorporated hereinby reference in their entirety.

FIELD OF THE INVENTION

The invention relates to the transmission of data between underwaterentities, particular at high data rates.

BACKGROUND

This Background section is provided for informational purposes only, andshould not be considered as an admission that any of the materialcontained in this section qualifies as prior art to the presentapplication.

There is a need for conveying data between two separate underwaterentities in applications including defense, oceanography, hydrocarbondevelopment, etc. Conventional methods for conveying data betweenunderwater entities employ either a tethered link using copper or fiberoptics, or rely on acoustic transmission. According to the formerapproach, the underwater entities must be repositioned or replaced insitu, while the latter approach has a very low data rate (1 to 20kilobits per second is typical) that is currently possible usingacoustic transmission. An approach that uses light propagating freely inthe ocean environment would provide much higher data rates and thepossibility of conveniently exchanging data between arbitrary pairs oftransmitting and receiving devices (transceivers).

Some attempts to implement data transmission between underwater entitiesusing optical means have been frustrated by a lack of suitable lightsources. The propagation of light through water is limited by thefundamental absorption properties of pure water, scattering ofparticulates such as plankton and inorganic particulates, and absorptionby chlorophyll-containing phytoplankton and other organic materials. Thecomponents combine, in various combinations, to favor strongly thetransmission of light in the blue-green region of the optical spectrum,approximately from 400 to 600 nm. The optical effect of the variouscombinations of the components admixed in water can be summarized aswater types and range from the very purest natural waters, which favordeep blue propagation (nominally 450 nm), to waters which favorblue-green (nominally 490 nm) and green (nominally 530 nm) propagation.The minimum optical attenuation coefficients at the optimal wavelengthsvary from about 0.02 m-1 for the very clearest natural waters, to morethan 2 m-1 in the most turbid coastal or harbor waters.

Previous light sources in the blue-green wavelength range have includedbeen bulky, inefficient, expensive and employed external modulators.

SUMMARY

At least one aspect of the present disclosure is direct to a device fortransmitting and receiving data optically through an aqueous medium. Insome embodiments, the device includes an optical transmitter. The devicecan also include an optical receiver. The transmitter and receiver canoperate using light with wavelengths in the range of 400 nm-600 nm.

In one embodiment, the optical transmitter and optical receiver of thedevice are enclosed in a waterproof container. The optical container caninclude one or more optical windows. Light can be transmitted throughthe one or more optical windows through the waterproof container andinto or out of the aqueous medium.

In one embodiment, the optical transmitter includes at least one solidstate light source.

In one embodiment, the light source is an InGaN based light source.

In one embodiment, the light source includes an LED.

In one embodiment, the light source includes a laser.

In one embodiment, the device is configured to transmit data at a rateof about 10 Mbps or greater.

In one embodiment, the device is configured to transmit data at a rateof about 100 Mbps or greater.

In one embodiment, the device includes a controller configured tomodulate the output of the light source. The controller can modulate theoutput of the light source by varying a drive current to the source.

In one embodiment, the optical receiver includes a photodiode.

In one embodiment, the optical receiver includes at least one from thelist consisting of: a silicon photodiode, silicon PIN photodiode, andavalanche photodiode, and a hybrid photodiode.

In one embodiment, the optical receiver includes a photomultiplier tube.

In one embodiment, the photomultiplier tube includes a plurality of gainstages. An output can be extracted from a gain stage prior to a finalgain stage.

In one embodiment, the optical receiver is configured to use ameasurement of the optical signal strength to control the gain of anamplifier following the optical detector.

In one embodiment, the optical receiver is configured to use ameasurement of the optical signal strength to control a gain of theoptical detector.

In one embodiment, the device includes at least one controlleroperatively coupled to one or both of the transmitter and receiver. Thecontroller can be configured to implement a channel coding techniqueduring transmission.

In one embodiment, the devices includes at least one controlleroperatively coupled to one or both of the transmitter and receiver. Thecontroller can be configured to dynamically adjust one or moretransmission parameters. The controller can dynamically adjust thetransmission parameters responsive to one or more detected transmissionconditions.

In one embodiment, dynamically adjusting one or more transmissionparameters includes controlling the gain of one or more amplifierelements in the device.

In one embodiment, the device includes at least one controlleroperatively coupled to one or both of the transmitter and receiver. Thecontroller can be configured to implement a multi-carrier transmissionmodulation techniques.

In one embodiment, the modulation technique can include optically basedOrthogonal Frequency Division Multiplexing (OFDM).

In one embodiment, the transceiver is configured to enter a power upstate in response to the detected presence of another data transmissiondevice.

In one embodiment, the device includes a controller configured to aligna local transceiver with a remote transceiver. The controller can alignthe local transceiver with the remote transceiver based on a signal fromthe one or more optical detectors that can sense the relative angle ofthe remote transceiver.

In one embodiment, the device includes a controller configured to aligna local transceiver with a remote transceiver based on a signal from oneor more sensors used to detect the relative position of the remotetransceiver.

In one embodiment, the controller is configured to control a platformfor the device based at least in part on the detected positioninformation.

In one embodiment, the device includes a controller configured tocontrol a plurality of transmitting sources to direct light to theremote transceiver. The controller can control the plurality oftransmitting sources based on a signal from one or more opticaldetectors used to sense the relative angle of the remote transceiver.

In one embodiment, the device includes a controller configured to selectan anode in a multiple-anode photomultiplier tube and align a localreceiver's angular field of view with the remote transceiver. Thecontroller can select the anode and align the local receiver's angularfield view based on a signal from one or more optical detectors are usedto sense the relative angle of a remote transceiver.

In one embodiment, the device includes a controller configured toprovide guidance commands to a platform on which the device is mounted.The one or more optical detectors can be used to sense the relativeangle of a remote transceiver.

In one embodiment, the device is incorporated in an all-optical systemfor transmission of seismic data.

In one embodiment, the one or more diffractive optical elements are usedto collect an optical transmission beam.

In one embodiment, the one or more diffractive optical elements are usedto steer an optical transmission beam.

In one embodiment, one or more diffractive optical elements are used toshape an optical transmission beam.

In one embodiment, the device is mounted on or in at least one from thelist consisting of: a remotely operated vehicle, an autonomouslyoperated vehicle, a submarine vessel, and an ocean bottom seismic node.

In one embodiment, the device includes an acoustic communication device.

At least one aspect is directed to a method that includes opticallytransmitting data through an aqueous medium using light with wavelengthsin the range of 400 nm-600 nm.

In one embodiment, the method includes generating the light using atleast one solid state light source.

In one embodiment of the method, the light source includes an LED.

In one embodiment, the light source includes a laser.

In one embodiment, the step of optically transmitting data includestransmitting data at a rate of at least about 10 Mbps.

In one embodiment, the step of optically transmitting data includestransmitting data at a rate of at least 100 Mbps.

In one embodiment, the step of optically transmitting data includesusing one or more channel coding techniques.

In one embodiment, the step of optically transmitting data includesdynamically adjusting one or more transmission parameters. Thetransmission parameters can be dynamically adjusted in response to oneor more detected transmission conditions.

In one embodiment, the step of optically transmitting data includesimplementing a multi-carrier transmission modulation technique.

In one embodiment, the modulation technique includes optically basedOrthogonal Frequency Division Multiplexing (OFDM).

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a block diagram showing operation of an exemplary pair oftransceivers in communication with each other.

FIG. 2 is an illustration of exemplary pairs of transceivers.

FIG. 3 is an illustration of receiver lenses and correspondingcircuitry.

FIGS. 4-8 are block diagrams of exemplary embodiments of transceivers.

DETAILED DESCRIPTION

Applicants have recognized that optical data transceivers may beprovided that operate in an aqueous medium. In some embodiments, thetransceivers operate with high data transfer rates, e.g., greater thanabout 1 megabyte per second (Mbps), about 10 Mbps, about 100 Mbps ormore.

In some embodiments, the devices use light sources, e.g., lasers lightsources or light emitting diode (“LED”) sources, with outputs in theblue-green region of the spectrum, e.g., with wavelengths in the rangeof 400-600 nm or any subrange thereof.

For example, in some embodiments, solid-state light emitters, e.g.,based upon the Indium-Gallium-Nitride (InGaN) semiconductor materialsnow provide a family of light sources in the blue-green spectral regionthat are efficient, compact, long-lived, and can be directly modulated(their optical output power controlled by the amount of electricalcurrent flow in the device). Such devices may operate at wavelengthsthroughout the blue-green region. Because these devices can be directlymodulated, e.g., by modulating a drive current, they can be arranged inarrays for increased output power or for transmission into other spatialdirections such as between platforms with relative movement.

In some embodiments, the receiver portion of the transceiver deviceincludes one or more optical detectors that are sensitive in theblue-green spectral region that may be compact and reliable. Examplesinclude detectors using semiconductor junctions such as PN junctions orPIN junctions (e.g., silicon PIN photodiodes or avalanche photodiodes).For example, in some embodiments, avalanche photodiodes may be usedthat, with the proper electrical bias voltage applied, exhibitelectronic gain, which can be useful in certain implementations.Photomultiplier tubes may also be used in the blue-green, and have theadvantage, like avalanche photodiodes, of voltage-dependent electronicgain, as well as fast temporal response even with large collectingareas.

In some embodiments, the optical detector's active or photosensitivearea places simultaneous constraints on the collecting area of areceiver lens and the angular field over which light intercepted by thereceiver lens actually lands on the detector (the angular field ofview). Under some applications, particularly where one or anotherunderwater platform is maneuvering, the angular field of view possiblewith temporally optimal detectors will be too small to maintain acommunication connection. Also, it may be useful to reduce the angularspread of the transmitter beam in order to increase the interceptedpower on a remote receiver. In this case it may be advantageous to mountthe transmitter and receiver on controllable mounts (e.g., gimbals), orto provide a mechanism (e.g., an electrical or electromechanicalmechanism) for the transmitter output beam and/or the receiver field ofview to follow a remote transmitter and receiver. Guidance commands forthe motion of the transmitter and receiver can be generated using, e.g.,a system of optical detectors or a multi-element detector withappropriate signal processing to interpret varying light levels from theremote transmitter and guide the direction of the transmitter beam andthe receiver field of view.

Referring to FIG. 1, an optical communication system that transmit datathrough an aqueous medium includes a first optical transceiver 10 and asecond optical transceiver 20. Each transceiver includes an opticaltransmitter 100 and an optical receiver 200. As shown, the opticaltransmitter 100 and an optical receiver 200 of transceiver 10 arepackaged together in a housing 300 to provide bi-directional datatransmission with a similarly packaged optical transceiver 20.

Each of the transceivers may be mounted on any suitable platformincluding an underwater vehicle (e.g., a submarine, remotely operatedvehicle, or autonomously operated vehicle), an underwater device (e.g.,an ocean bottom seismic node, such as the types available fromFairfieldNodal, Inc. of Sugarland, Tex.), an underwater structure (e.g.,an oil drilling or pumping platform), or any other suitable object.

A transmitter and receiver packaged together are referred to as atransceiver. Although the embodiments shown focus on transceiverpackages, it is to be understood that in various embodiments, thetransmitter and receiver may be separately packaged. In someembodiments, a single transmitter in a single receiver may be used foruni-directional communication.

As shown in FIG. 1, simultaneous bi-directional data transmission may beaccomplished by the use of spectrally separated wavelengths, so that thetransmitter of transceiver one may transmit a wavelength 1 (for example,a blue wavelength or band of wavelengths, such as might be emitted by anInGaN LED) and the transmitter of transceiver 2 transmits a wavelength 2for example, a blue-green or green wavelength or band of wavelengths).The receiver of transceiver 2 will be configured to receive thewavelength 1 of transmitter 1 and reject the wavelength 2 of transmitter2 and all or as many as possible wavelengths outside the band ofwavelength 1 using optical filters. Other data transmission schemes maybe employed as well. For example, instead of separating the upstream anddownstream signals by wavelength, they may instead be transmitted usingtime-division multiplexing or by polarization. Similarly, code-divisionmultiplexing and other data transmission schemes may be used.

Various embodiments include the capacity to incorporate multi-carriertransmission modulation techniques such as optically based OrthogonalFrequency Division Multiplexing (OFDM). Many closely spaced subcarriersare utilized to increase the overall transmission rate. The optical datacan also be transmitted using coherent OFDM, CO-OFDM, protocols usingsingle carrier or multicarrier transmission schemes.

Similarly receiver of transceiver 1 may be configured to receivewavelength 2 of transmitter 2 and reject the wavelength of transmitter 1and all or as many as possible wavelengths outside of the band ofwavelength 2.

Another embodiment, shown in FIG. 2, provides for bidirectionaltransmission by spatial separation of the respective transmitters andreceivers. Here the transmitter 1 of transceiver 1 is aligned (e.g.,closely aligned) with receiver 2 of transceiver 2, and the transmitter 2of transceiver 2 is aligned (e.g., closely aligned) with the receiver 2of transceiver 2, so as to prevent light emitted by transmitter 1 butscattered by the intervening aqueous medium from entering receiver 1,and similarly the light from transmitter 2 but scattered by theintervening aqueous medium is unable to enter receiver 2.

Various embodiments may include one or more mechanisms to direct theoutput light from a transmitter in the direction of a receiver and/or tocause the field of view of a receiver to track the output of atransmitter. In addition to mechanical scanning of the transmitter andreceiver to change the pointing direction, electronic systems may alsobe used. An electronic system capable of scanning the transmitterdirection may arrange a plurality of individual light sources (e.g. LEDsor lasers), or a plurality of arrays of light sources, pointing indifferent directions so that the device or array pointing in thedirection of interest can be used to transmit the data, as shown in FIG.2. In this way the power consumption of the transceiver can besignificantly reduced compared to a system that transmits power into alarger angular field of view.

For example, FIG. 3 shows an electronic mechanism for scanning thereceiver field of view using a multiple-anode photomultiplier tube, inwhich separate gain-producing dynode arrays and anodes are provided in aone- or two-dimensional arrangement such that light striking a spatiallocation on the photocathode produces an electrical signal at the anodecorresponding to the photocathode spatial location. By placing themultiple-anode photomultiplier tube at the focus of a lens the angularposition of the remote transmitter beam is converted into a spatiallocation on the photocathode. This receiver can serve a dual purpose;sensing the location of the remote transmitter for guidance; and byselecting only the anode corresponding to the photocathode locationwhere the transmitter signal is detected a specific field of view can beobtained, as in FIG. 2, thereby rejecting interfering light sources.

The components of an exemplary optical transceiver are now describedwith reference to FIG. 4. The transmitter 100 comprises a series ofelectronic components used to convert an incoming data signal into anoutgoing optical signal that can be transmitted through the aqueousmedium. A data signal is conducted to a data conversion module 110,which converts the incoming data, typically conveyed using either aconducting cable or a fiber-optic cable, into an on-off keyed format,such as 8 b/10 b encoding or pulse-position modulation, which isappropriate for use by the transmitter. This module may typically alsoprovide the functions of ascertaining whether a data connection ispresent on the cable side, and in turn provide a signaling format thatthe transmitter can transmit to a remote receiver so as to alert theremote transceiver as to its presence. The output of the data conversionmodule 110 is conveyed to a transmitter drive module 120, which receivesthe output of the data conversion module 110 and by use of amplifiersand other electronic components converts the output of the dataconversion module 110 into a drive signal for the light source 130,either singly or in a plurality (e.g., an array), such that the opticaloutput of the light source 130 varies between a lower optical powerstate (e.g., with little or no optical output) and a higher opticalpower state.

The electronic circuits of the transmitter drive module 120 may bedesigned so as to maintain as much fidelity as possible between thetemporal characteristics (pulse width, risetime and falltime) of theelectronic output waveform of the data conversion module 110 and theoptical output waveform of the light source 130. This may require acombination of electronic feedback within the amplifier circuits,temperature compensation to correct for temperature-induced changes inthe optical output of the light source 130 for a given electricalcurrent conveyed from the transmitter drive module 120, or opticalfeedback from the light source 130 into circuits associated with thetransmitter drive module 120 such that the optical waveform exhibitsmaximum fidelity to the input electrical waveform.

As noted above, the light source may be, for example, an LED source or alaser source, such as an InGaN based LED or current driven solid statelaser such as an InGaN laser. The choice of whether an LED or laser isused will depend largely on the data bandwidth required. In someembodiments, it may be difficult to achieve to achieve data bandwidthsof much greater than 10 or 20 Mbps using LEDs due to carrier-lifetimeeffects in the PN junction leading to long temporal decays of theoptical output.

In contrast, laser sources may operate with a significantly shortertemporal pulse width. In some embodiments this is because when the drivecurrent to the laser drops below a threshold level, lasing ceases, andthe output intensity of the laser rapidly decreases. Similarly, as thedrive current increases across the lasing threshold, the outputintensity of the laser may rapidly increase. Accordingly, the modulatedlaser output may reproduce even a rapidly modulated drive signal withvery high fidelity. Accordingly, in some embodiments, a data ratetransmission rate of greater than 10 Mbps, 50 Mbps, 75 Mbps, 100 Mbps,200 Mbps, 300 Mbps, 400 Mbps, 500, Mbps, 600 Mbps, 1000 Mbps or more maybe provided.

The optical output of the light source may be modified in angular extentby use of an optical element 140. The optical element 140 may be, forexample, a transparent epoxy lens integral to an LED or diode laser inan industry-standard package, or, particularly in the case of a laser inlieu of an LED, this external element may be a lens or other refractive,reflective, or diffractive element as required to shape the transmitterbeam into the desired angular field.

A power supply 170 is provided to condition input power from theplatform hosting the transmitter 100 and provide the required voltagesand currents to power the various electronic modules of the transmitter100. This power supply 170 may typically be a high-efficiency, low-noiseswitching supply, with one or more outputs.

The receiver 200 of the optical transceiver will generally comprise anoptical element 210 which collects incoming light and directs it to thephotosensitive area of an optical detector 230. The optical element 210may be a spherical or aspherical lens, or another reflective,refractive, or diffractive optical element (or grouping of elements)selected so as to match the desired angular field and collecting areawith the photosensitive area of the detector. In one embodiment a fieldlens may be added following the optical element 210 in order toilluminate the surface of the optical detector 230 more uniformly.

An optical filter 220 (or any other suitable wavelength selectiveelements) will either precede the optical element 210 (be placed on theside towards the remote transmitter 100) or follow the optical element210 but precede the optical detector 230. The purpose of the opticalfilter is to as completely as possible transmit only the opticalwavelength or wavelengths corresponding to those emitted by the remotetransmitter 100 and to reject as completely as possible the wavelengthor wavelengths emitted by an adjacent transmitter, as well as ambientsunlight and other extraneous light. The optical filter 220 maytypically be a colored (absorbing) glass filter, a colored (absorbing)plastic filter, or an interference (reflecting) filter or wavelengthdiffractive element, as appropriate to the required optical bandwidth,rejection and angular acceptance.

The optical detector 230 converts the light collected by optical element210 and transmitted by optical filter 220 into an electrical signal forfurther processing. The optical detector is followed by an amplifiermodule 240. In one embodiment the optical detector 230 may be asemiconductor detector such as a silicon PIN photodiode. In thisembodiment the amplifier module 240 comprises a preamplifier and anautomatic gain control amplifier to amplify the electrical output of thephotodiode to match the electrical output to electronic stages. A powersupply 235 provides a low bias voltage to the PIN photodiode to reduceshunt capacitance and improve temporal response.

In some embodiments, e.g., as illustrated in FIG. 5, using an avalanchephotodiode as the optical detector 230 the power supply 235 would be ofa higher voltage to drive the photodiode into the avalanche regime andprovide electronic gain. In this embodiment the power supply 235 wouldtypically have a temperature sensor (such as a thermistor) to monitorthe avalanche photodiode temperature and automatically adjust thevoltage output to compensate for temperature dependence in the avalanchevoltage of the avalanche photodiode. In this embodiment the amplifiermodule 240 may also provide a small fraction of the amplified electricalsignal to an automatic gain control module 250 which integrates theelectrical signal, conditions it and supplies it to a voltage-controlinput of the power supply 235, thereby controlling the voltage of thepower supply 235 and thereby the gain of the avalanche photodiode tomatch varying light levels received at the optical detector 230 due toreceived transmitter light or other detected light.

The automatic gain control module may itself, e.g., in its own internalcircuits, include variable gain to keep the output signal within therequired range for subsequent processing (such as in the demodulationmodule 260).

In an embodiment using a photomultiplier tube the as the opticaldetector 230 a power supply 235 supplies high voltage (100-500V typical)to the photomultiplier tube in order to provide fast temporal responseand electronic gain. Typically the power supply 235 in this embodimentwill have a voltage control input, as in an embodiment using theavalanche photodiode, so that a similar automatic gain control module250 can control the voltage supplied to the photomultiplier tube andthereby its electronic gain to match varying light levels received atthe optical detector 230 due to received transmitter light or otherdetected light, as well as to protect the photomultiplier tube fromdamage due to high light levels.

In an embodiment that uses a photomultiplier tube at data rates above,e.g., 100 Mbps, such as 622 Mbps or 1000 Mbps, special consideration maybe taken with the choice of photomultiplier tube. A very high bandwidthtube may be required, and particular care may be needed in itsoperation. For example, it may be necessary to utilize only the firstfew stages of a conventional high-speed photomultiplier tube, drawingthe signal current from an intermediate dynode stage, rather than fromthe anode, in order to obtain fast enough rise and fall times to supportthe high bit rate. In an additional embodiment a photomultiplier tubewhich uses a micro-channel plate as the electronic gain medium in lieuof a conventional dynode structure may be used. In a further embodiment,a hybrid photodiode may be used, a device which combines a vacuum stageoperating at high voltage followed by an internal semiconductoravalanche structure may be used to provide a significant photosensitivearea and electronic gain while supporting the bandwidth required for,e.g., 1000 Mbps operation. In another embodiment, a vacuum photodiode,which provides a large collecting area and high speed without internalelectronic gain may be used, provided that sufficient gain can beprovided in subsequent electronic amplification stages.

The output of the amplifier module 240 is conveyed to a demodulationmodule 260 which detects the amplified waveform using a waveformdetection module which may include, e.g., Schmidt triggers, clocks andother circuits to convert the detected waveform into a signal that canbe conveyed to the data conversion module 270 which converts the dataformat created by the demodulation module 260 from the detected opticalwaveform into a data format useable for an external data recipientlocated on the host platform.

A power supply 280 is provided to condition input power from theplatform hosting the transmitter 100 and provide the required voltagesand currents to power the various electronic modules of the receiver200. This power supply 280 may typically be a high-efficiency, low-noiseswitching supply, with one or more outputs.

In the case of infrequent data exchanges, a power control module 290,which uses an optical detector and a low-powered circuit with anamplifier, electronic filter, a threshold circuit and a relay orelectronic switch may be provided to sense the proximity of a remotetransmitter and activate the local transmitter and receiver byconnecting the input power between the power supply 170 (shown in FIG.4)/power supply 280 and the power source on the platform.

In the embodiment illustrated in FIG. 1 the transmitter 100 and thereceiver 200 will be collocated in a pressure vessel 300 in order toisolate the transmitter 100 and receiver 200 from contact with theaqueous environment. In this embodiment windows 310 will be provided toconvey light from the transmitter 100 into the aqueous medium and to aremotely mounted receiver, and from a remotely mounted transmitterthrough the aqueous medium to the receiver 200. These may typically beseparate windows for the transmitter and receiver, but can also be asingle window serving both transmitter and receiver.

In an embodiment in which the directions of the transmitter beam and/orreceiver field of view must be moved during operation (such as forcommunication between a moving and a stationary transceiver) an elementis provided that senses the direction of a remote transmitter andgenerates control signals for a gimbal or other mechanical device thattranslates the pointing angle of the transmitter or receiver, or for anelectronic pointing angles translator. FIG. 6 shows one embodiment,useful for the case where the angular directions must be controlled inone dimension only, in which an array of optical detectors 410 arepointed in different angles to sense the incoming transmitter beam. Theoptical detectors are provided with optical filters 415 (or otherwavelength selective elements) to transmit light from the remotetransmitter and reject backscattered light from the local transmitter.The optical detectors may also be provided with lenses 420 or anotheroptical element capable of defining the optical detector field of view.The electrical signal from the optical detectors 410 is conveyed to anamplifier module 440. The amplifier module 440 will typically includeautomatic gain control in order to maintain the output signal within therange of voltage levels useable by following stages. The electricaloutput from the optical detectors is conveyed to a guidance processormodule 460 which measures the signal strength from each optical detectorand calculates the direction of the remote transmitter. The calculationcan be accomplished for coarse direction by taking the ratios of thestrengths of the optical signals using either a system of operationalamplifiers or by using an actual analog to digital conversion andperforming the calculation in a microprocessor system. A more precisecalculation of the direction of the remote transmitter can beaccomplished in a microprocessor by taking into account the geometry ofthe detectors and the amount of remote transmitter light that will beintercepted by them as a function of angle.

Another embodiment illustrated in FIG. 7 uses a position-sensitiveoptical detector 520 such as a position-sensing semiconductor photodiode(e.g., a split photodiode), position-sensing (e.g., resistive anode)photomultiplier tube, or a multiple-anode photomultiplier tube with avoltage divider circuit to provide the angular location of the remotetransmitter. An imaging optical element 410 such as a lens is used toconvert the angle of the incoming transmitter light into a position onthe active area of the positions-sensitive optical detector 520. Anoptical filter 415 can be used to transmit light from the remotetransmitter and reject ambient background light and backscattered localtransmitter light. The electrical output of the position-sensitivedetector 520 is conveyed to an amplifier module 440 and the output ofthe amplifier module 440 conveyed to a guidance processor module 460 forthe generation of guidance signals. The guidance signals generated fromthis embodiment are accurate enough for precision platform guidance, ifneeded.

In addition to wavelength-selective optical filter 415, in order toreject background light (such as sunlight when the transceivers areshallow) an electronic filter may be included either in the amplifiermodule 440 or in the guidance processor module 460 in order to rejectsteady or slowly varying (un-modulated) optical signals and accept themodulated signal from the remote transmitter.

The output of the guidance processor module 460 is conveyed to a drivemodule 470 which provides electrical signals to a motor driven gimbal480 (or other positioning device) on which are mounted the transmitterand receiver such that an electrical signal from the drive module 470translates the angle of the transmitter and receiver relative to thehousing. A power supply 490 is provided to condition power from theplatform and provide the required voltages and currents to therespective modules.

Another embodiment illustrated in FIG. 8 uses the output of the guidanceprocessor module 460 to select angularly separated transmitter lightsources or light source arrays 610 so as to project a transmitter beaminto the desired direction. Another embodiment uses the output of theguidance processor to switch the output of a multiple-anodephotomultiplier tube used as the optical detector so as to select thedirection for which an incoming light beam will be sensed.

In some embodiments, the transceivers described herein may use channelcoding techniques to increase link robustness and transmission rates.For example, low-density parity-check, LDPC, codes and rate adaptivechannel codes may be used.

In some embodiments, the transceivers described herein may implementdynamic optimization of the transmission parameters. In underwaterenvironments such as seismic sensing, the local water conditions canvary significantly. In order to accommodate the variation the opticallinks are dynamically configured to measure link loss mechanisms, aloneor in combinations with other effects such as dispersion, and assign anoptimal data rate. In addition, if the underwater environmentalconditions permit, multi-carrier modes can be initiated. Local DigitalSignal Processing, DSP, can be performed to adjust or compensate for theapplicable transmission-reception parameters, or software can implementthe communication control adjustments. The optical transmission receiverlinkage can be monitored continuously in order to maintain linkperformance.

In some embodiments, receivers of the type herein may be used totransmit seismic data, e.g., from an autonomous underwater seismic nodeto a retrieval device. The retrieval device may be mounted on, forexample, an submarine vessel, a remotely operated vehicle, or anautonomously operated vehicle. In some embodiments, the seismic datatransfer may be performed at a rate of at least 10 Mbps, 100 Mbps, 500Mbps, 1000 Mbps or more. In some embodiments, the transmission link ismaintained for at least 1 second, 10 seconds, 1 minutes, 5 minutes, 10minutes, 20 minutes, 30 minutes, 40 minutes, 50 minutes, 1 hour, ormore. In some embodiments, the transmission occurs over a distance of atleast 10 cm, 100 cm, 1 m, 2 m, 3 m, 5 m, 10 m, 20 m, 100 m or more.

Although in many embodiments (e.g., as described herein) it isadvantageous to used wavelengths in the range of 400-600 nm (or anysubrange thereof), in other cases depending on the application at handany other suitable wavelengths may be used (e.g., wavelengths in therange of 300 nm to 1400 nm).

While various inventive embodiments have been described and illustratedherein, those of ordinary skill in the art will readily envision avariety of other means and/or structures for performing the functionand/or obtaining the results and/or one or more of the advantagesdescribed herein, and each of such variations and/or modifications isdeemed to be within the scope of the inventive embodiments describedherein. More generally, those skilled in the art will readily appreciatethat all parameters, dimensions, materials, and configurations describedherein are meant to be exemplary and that the actual parameters,dimensions, materials, and/or configurations will depend upon thespecific application or applications for which the inventive teachingsis/are used. Those skilled in the art will recognize, or be able toascertain using no more than routine experimentation, many equivalentsto the specific inventive embodiments described herein. It is,therefore, to be understood that the foregoing embodiments are presentedby way of example only and that, within the scope of the appended claimsand equivalents thereto, inventive embodiments may be practicedotherwise than as specifically described and claimed. Inventiveembodiments of the present disclosure are directed to each individualfeature, system, article, material, kit, and/or method described herein.In addition, any combination of two or more such features, systems,articles, materials, kits, and/or methods, if such features, systems,articles, materials, kits, and/or methods are not mutually inconsistent,is included within the inventive scope of the present disclosure.

The above-described embodiments can be implemented in any of numerousways. For example, the embodiments may be implemented using hardware,software or a combination thereof. When implemented in software, thesoftware code can be executed on any suitable processor or collection ofprocessors, whether provided in a single computer or distributed amongmultiple computers.

Also, a computer may have one or more input and output devices. Thesedevices can be used, among other things, to present a user interface.Examples of output devices that can be used to provide a user interfaceinclude printers or display screens for visual presentation of outputand speakers or other sound generating devices for audible presentationof output. Examples of input devices that can be used for a userinterface include keyboards, and pointing devices, such as mice, touchpads, and digitizing tablets. As another example, a computer may receiveinput information through speech recognition or in other audible format.

Such computers may be interconnected by one or more networks in anysuitable form, including a local area network or a wide area network,such as an enterprise network, and intelligent network (IN) or theInternet. Such networks may be based on any suitable technology and mayoperate according to any suitable protocol and may include wirelessnetworks, wired networks or fiber optic networks.

A computer employed to implement at least a portion of the functionalitydescribed herein may comprise a memory, one or more processing units(also referred to herein simply as “processors”), one or morecommunication interfaces, one or more display units, and one or moreuser input devices. The memory may comprise any computer-readable media,and may store computer instructions (also referred to herein as“processor-executable instructions”) for implementing the variousfunctionalities described herein. The processing unit(s) may be used toexecute the instructions. The communication interface(s) may be coupledto a wired or wireless network, bus, or other communication means andmay therefore allow the computer to transmit communications to and/orreceive communications from other devices. The display unit(s) may beprovided, for example, to allow a user to view various information inconnection with execution of the instructions. The user input device(s)may be provided, for example, to allow the user to make manualadjustments, make selections, enter data or various other information,and/or interact in any of a variety of manners with the processor duringexecution of the instructions.

The various methods or processes outlined herein may be coded assoftware that is executable on one or more processors that employ anyone of a variety of operating systems or platforms. Additionally, suchsoftware may be written using any of a number of suitable programminglanguages and/or programming or scripting tools, and also may becompiled as executable machine language code or intermediate code thatis executed on a framework or virtual machine.

In this respect, various inventive concepts may be embodied as acomputer readable storage medium (or multiple computer readable storagemedia) (e.g., a computer memory, one or more floppy discs, compactdiscs, optical discs, magnetic tapes, flash memories, circuitconfigurations in Field Programmable Gate Arrays or other semiconductordevices, or other non-transitory medium or tangible computer storagemedium) encoded with one or more programs that, when executed on one ormore computers or other processors, perform methods that implement thevarious embodiments of the invention discussed above. The computerreadable medium or media can be transportable, such that the program orprograms stored thereon can be loaded onto one or more differentcomputers or other processors to implement various aspects of thepresent invention as discussed above.

The terms “program” or “software” are used herein in a generic sense torefer to any type of computer code or set of computer-executableinstructions that can be employed to program a computer or otherprocessor to implement various aspects of embodiments as discussedabove. Additionally, it should be appreciated that according to oneaspect, one or more computer programs that when executed perform methodsof the present invention need not reside on a single computer orprocessor, but may be distributed in a modular fashion amongst a numberof different computers or processors to implement various aspects of thepresent invention.

Computer-executable instructions may be in many forms, such as programmodules, executed by one or more computers or other devices. Generally,program modules include routines, programs, objects, components, datastructures, etc. that perform particular tasks or implement particularabstract data types. Typically the functionality of the program modulesmay be combined or distributed as desired in various embodiments.

Also, data structures may be stored in computer-readable media in anysuitable form. For simplicity of illustration, data structures may beshown to have fields that are related through location in the datastructure. Such relationships may likewise be achieved by assigningstorage for the fields with locations in a computer-readable medium thatconvey relationship between the fields. However, any suitable mechanismmay be used to establish a relationship between information in fields ofa data structure, including through the use of pointers, tags or othermechanisms that establish relationship between data elements.

Also, various inventive concepts may be embodied as one or more methods,of which an example has been provided. The acts performed as part of themethod may be ordered in any suitable way. Accordingly, embodiments maybe constructed in which acts are performed in an order different thanillustrated, which may include performing some acts simultaneously, eventhough shown as sequential acts in illustrative embodiments.

All definitions, as defined and used herein, should be understood tocontrol over dictionary definitions, definitions in documentsincorporated by reference, and/or ordinary meanings of the definedterms.

The indefinite articles “a” and “an,” as used herein in thespecification and in the claims, unless clearly indicated to thecontrary, should be understood to mean “at least one.”

The phrase “and/or,” as used herein in the specification and in theclaims, should be understood to mean “either or both” of the elements soconjoined, i.e., elements that are conjunctively present in some casesand disjunctively present in other cases. Multiple elements listed with“and/or” should be construed in the same fashion, i.e., “one or more” ofthe elements so conjoined. Other elements may optionally be presentother than the elements specifically identified by the “and/or” clause,whether related or unrelated to those elements specifically identified.Thus, as a non-limiting example, a reference to “A and/or B”, when usedin conjunction with open-ended language such as “comprising” can refer,in one embodiment, to A only (optionally including elements other thanB); in another embodiment, to B only (optionally including elementsother than A); in yet another embodiment, to both A and B (optionallyincluding other elements); etc.

As used herein in the specification and in the claims, “or” should beunderstood to have the same meaning as “and/or” as defined above. Forexample, when separating items in a list, “or” or “and/or” shall beinterpreted as being inclusive, i.e., the inclusion of at least one, butalso including more than one, of a number or list of elements, and,optionally, additional unlisted items. Only terms clearly indicated tothe contrary, such as “only one of” or “exactly one of,” or, when usedin the claims, “consisting of,” will refer to the inclusion of exactlyone element of a number or list of elements. In general, the term “or”as used herein shall only be interpreted as indicating exclusivealternatives (i.e. “one or the other but not both”) when preceded byterms of exclusivity, such as “either,” “one of,” “only one of,” or“exactly one of.” “Consisting essentially of,” when used in the claims,shall have its ordinary meaning as used in the field of patent law.

As used herein in the specification and in the claims, the phrase “atleast one,” in reference to a list of one or more elements, should beunderstood to mean at least one element selected from any one or more ofthe elements in the list of elements, but not necessarily including atleast one of each and every element specifically listed within the listof elements and not excluding any combinations of elements in the listof elements. This definition also allows that elements may optionally bepresent other than the elements specifically identified within the listof elements to which the phrase “at least one” refers, whether relatedor unrelated to those elements specifically identified. Thus, as anon-limiting example, “at least one of A and B” (or, equivalently, “atleast one of A or B,” or, equivalently “at least one of A and/or B”) canrefer, in one embodiment, to at least one, optionally including morethan one, A, with no B present (and optionally including elements otherthan B); in another embodiment, to at least one, optionally includingmore than one, B, with no A present (and optionally including elementsother than A); in yet another embodiment, to at least one, optionallyincluding more than one, A, and at least one, optionally including morethan one, B (and optionally including other elements); etc.

In the claims, as well as in the specification above, all transitionalphrases such as “comprising,” “including,” “carrying,” “having,”“containing,” “involving,” “holding,” “composed of,” and the like are tobe understood to be open-ended, i.e., to mean including but not limitedto. Only the transitional phrases “consisting of” and “consistingessentially of” shall be closed or semi-closed transitional phrases,respectively, as set forth in the United States Patent Office Manual ofPatent Examining Procedures, Section 2111.03

What is claimed is:
 1. A system to optically transfer seismic datathrough an aqueous medium, comprising: a retrieval device comprising: afirst optical transmitter to transmit light; a first optical receiver;one or more optical detectors to sense a relative angle of a secondoptical transmitter of an ocean bottom seismic (“OBS”) node; and atleast one controller configured to: select, based on a signal from theone or more optical detectors of the retrieval device, an anode in amultiple-anode photomultiplier tube; and align an angular field of viewof the first optical receiver with the second optical transmitter of theOBS node.
 2. The system of claim 1, wherein the OBS node comprises: asecond optical receiver comprising one or more optical detectors todetect a presence of the retrieval device and sense a relative angle ofthe first optical transmitter of the retrieval device.
 3. The system ofclaim 1, wherein the OBS node comprises: a second optical receivercomprising one or more optical detectors to detect a presence of theretrieval device and sense a relative angle of the first opticaltransmitter of the retrieval device; and one or more controllers toadjust a transmission parameter used by the second optical transmitterto transmit light with the seismic data, and control the second opticaltransmitter to direct the light with the seismic data through theaqueous medium to the first optical receiver of the retrieval device. 4.The system of claim 1, wherein the OBS node comprises: a second opticalreceiver comprising one or more optical detectors to detect a presenceof the retrieval device and sense a relative angle of the first opticaltransmitter of the retrieval device; one or more controllers to adjust atransmission parameter used by the second optical transmitter totransmit light with the seismic data, and control the second opticaltransmitter to direct the light with the seismic data through theaqueous medium to the first optical receiver of the retrieval device;and the second optical transmitter to enter a power up state responsiveto detection, by the second optical receiver, of the presence of theretrieval device, and transmit the light with the seismic data throughthe aqueous medium using the transmission parameter adjusted by the oneor more controllers, the light with the seismic data directed towardsthe first optical receiver through the aqueous medium by the one or morecontrollers.
 5. The system of claim 1, comprising: the first opticalreceiver of the retrieval device to receive the light with the seismicdata transmitted through the aqueous medium by the second opticaltransmitter of the OB S node.
 6. The system of claim 1, comprising: aphotodiode of the first optical receiver that generates electricaloutput based on the light with the seismic data transmitted by thesecond optical transmitter and received by the first optical receiver.7. The system of claim 1, comprising: a second optical retrievercomprising one or more optical detectors to detect a presence of theretrieval device based on the light transmitted by the first opticaltransmitter of the retrieval device.
 8. The system of claim 1, whereinthe OBS node comprises: a second optical receiver comprising one or moreoptical detectors to detect a presence of the retrieval device and sensea relative angle of the first optical transmitter of the retrievaldevice; and one or more controllers to: adjust a transmission parameterused by the second optical transmitter to transmit light with theseismic data, and control the second optical transmitter to direct thelight with the seismic data through the aqueous medium to the firstoptical receiver of the retrieval device; and select, based on a signalfrom the one or more optical detectors of the OBS node, an anode in amultiple-anode photomultiplier tube.
 9. The system of claim 1,comprising: the retrieval device to receive the seismic data from theOBS node placed on an ocean bottom, and store the seismic data in memoryof the retrieval device.
 10. The system of claim 1, wherein the OBS nodecomprises: one or more controllers to adjust a transmission parameterused by the second optical transmitter to transmit light with theseismic data, and control the second optical transmitter to direct thelight with the seismic data through the aqueous medium to the firstoptical receiver of the retrieval device based on the relative angle ofthe first optical transmitter of the retrieval device sensed by the oneor more optical detectors.
 11. The system of claim 1, wherein the secondoptical transmitter comprises a solid state light sources comprising atleast one of an InGaN based light source, an LED, and a laser.
 12. Thesystem of claim 1, wherein the OBS node comprises: one or morecontrollers to adjust, responsive to identification of an underwaterenvironmental condition, a transmission parameter used by the secondoptical transmitter to transmit light with the seismic data.
 13. Thesystem of claim 1, wherein the OBS node comprises one or morediffractive optical elements to steer an optical transmission beamtowards the retrieval device.
 14. A method of optically transferringseismic data through an aqueous medium, comprising: transmitting, by aretrieval device comprising a first optical transmitter and a firstoptical receiver, light; sensing, by one or more optical detectors ofthe retrieval device, a relative angle of a second optical transmitterof an ocean bottom seismic (“OBS”) node; selecting, by at least onecontroller of the retrieval device, based on a signal from the one ormore optical detectors of the retrieval device, an anode in amultiple-anode photomultiplier tube; and aligning, by the at least onecontroller of the retrieval device, an angular field of view of thefirst optical receiver with the second optical transmitter of the OBSnode.
 15. The method of claim 14, comprising: detecting, by the OBS nodecomprising a second optical receiver having one or more opticaldetectors, a presence of the retrieval device.
 16. The method of claim14, comprising: adjusting, by one or more controllers of the OBS node, atransmission parameter used by the second optical transmitter totransmit light with the seismic data.
 17. The method of claim 14,comprising: controlling, by one or more controllers of the OBS node, thesecond optical transmitter to direct the light with the seismic datathrough the aqueous medium to the first optical receiver of theretrieval device.
 18. The method of claim 14, comprising: detecting, bythe OBS node comprising a second optical receiver having one or moreoptical detectors, a presence of the retrieval device; entering, by thesecond optical transmitter of the OBS node, a power up state responsiveto detection, by the second optical receiver, of the presence of theretrieval device.
 19. The method of claim 14, comprising: transmitting,by the second optical transmitter of the OBS node, the light with theseismic data through the aqueous medium using a transmission parameteradjusted by the at least one controller, the light with the seismic datadirected towards the first optical receiver through the aqueous mediumby one or more controllers.
 20. The method of claim 14, comprising:receiving, by the first optical receiver of the retrieval device, thelight with the seismic data transmitted through the aqueous medium bythe second optical transmitter of the OBS node.